Talk:Sunset/Archive 1

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To User:Andycjp: I Don't really understand why this quote is in here:

In Judaism and Christianity they are considered to be evidence of the existence of God:
" The heavens are telling the glory of God..." (Psalm 19:1)

Despite being a Catholic like you, I have never heard this before. The Psalm 19 quote is not clearly related (it tells of the glory, meaning that God is taken on faith already), and devoid of context: the rest of the psalm mentions nothing about the sunset. What is the source of the argument, beside the fact that change implies a first cause. Also, non-Catholic sects often argue that the existence of God cannot be proved, so be careful in making broad generalizations about Christian faith. I have removed it until there is a better reason for including it.

I think we should move the pictures to a more pictures page. Chmouel 08:47, 26 Sep 2004 (UTC)

Do we have a standard way to arrange gallery articles? We could use one. ✏ Sverdrup 13:56, 26 Sep 2004 (UTC)

I don't think anybody come up where any gallery way. But we can do it as the list of image style and add a category there Chmouel 14:13, 26 Sep 2004 (UTC)

Recent changes (28 Jan 2005)

Can this possibly be true? From the article:

"... however in the Northern Hemisphere (for example), the earliest sunset is not at the winter solstice around December 21, but rather in early December. Likewise, the latest sunset is not around June 21 (the summer solstice), but in early July. (The dates may be swapped for sunset timings in the Southern Hemisphere.) For one or two weeks surrounding both solstices, both sunrise and sunset get slightly later each day."

Surely the timing of sunset would depend much more on the position of a location within its time zone, not to mention whether daylight savings time was in effect. Could someone please comment, if only to set me straight?

Reply: The date of the earliest and latest sunsets are based on the dates when the distances between the sun and earth's sunset-terminator line are at their absolute maxima and minima. The latest sunset in the Northern Hemisphere (say Fargo, ND) occurs on 6/27 at 9:25 PM this year (2007). This occurs on a later date than the summer solstice because the earth's orbit around the sun is elliptical, not circlular. The elliptical shape and the earth's 23 degree tilt causes the distance between the sun and the terminator line (sunset on earth) to be at its annual minimum (in the Northern Hemisphere) after the summer solstice. The earliest sunset in Fargo ND occurs st 4:38 PM on 12/11/2007. Again, because the earth's orbit is elliptical, the date of the earliest sunset occurs before the Winter Solstice, when the distance between the sun and the sunset terminator line on the earth is at it's annual maximum (in the Northern Hemisphere). The same geometric principles apply to the annual earliest and latest sunrises: Latest sunrise for Fargo, ND in the coming year: 1/2/2008 at 8:12 AM; the earliest sunrise for Fargo, ND in the coming year: 6/16/2007 at 5:32 AM. 201.160.124.221 00:29, 20 March 2007 (UTC)The Good Doctor Fry201.160.124.221 00:29, 20 March 2007 (UTC)

I am also uncertain of the truth of the statement:

"... because the light from the Sun is bent by the variable density of the Earth's atmosphere, the Sun is still seen after it is below the horizon. This effect is a daily illusion along with sunrise."

I imagine that this is in fact strictly true, but could someone knowledgable comment on this also?

Reply: Variability in density of the Earth's atmosphere doesn't really seem like the best way of explaining the phenomenon. The earth's atmosphere has a different index of refraction than the relative vacuum of space. The thickness of the earth's atmosphere is relatively thin, compared to the diameter of the earth. This spherically curved thin layer of air acts exactly like a thin lense, especially at sunrise and sunset. It gather's some of the sun's rays just before sunrise, and bends them downwards towards the observer, causing the sun to be visible to the observer before it physically rises above the horizon. The sunlight's path length through the thin lense of the atmosphere is longest at sunrise and sunset, so, the lensing effects are greatest at these two points. When the sun rises well above the horizon, the sunlight's path length through the atmosphere is relatively short and gives essentially constant lensing effects(sunlight's pathlength is at it's minima when the sun is directly overhead - not necessarily noon). So, it's really the size/length/magnitude of the sunlight's pathlength through the earth's atmosphere that causes these lensing effects. The Density of the Earth's Atmosphere does not change much, except for weather, dust, etc, but the number of air atoms and molecules in the viewing path between an observer on earth and the sun is at it's maxima at sunrise and sunset, so, in a perverse sort of calculation, you could say that the density of atoms and molecules calculated using the whole distance between sun and earth changes at sunrise and sunset (a somewhat peculiar way of calculating the lensing effect).

Now, variable density due to temperature fluctuations in the earth's atmosphere DOES affect the appearance of stars, causing them to appear to twinkle... (as evidenced by less twinkling when little heat or very constant amounts of heat is rising at night versus lots of twinkling after a hot day when lot's of heat rises off different colored surfaces at different rates causes thermal lensing - exactly like seeing "waves of hot air" rising off asphalt pavement on a hot day, distorting the images behind the waves. Also, again, path length through the earth's atmosphere plays a significant role here too, causing stars of the same magnitude of luminosity to appear to twinkle more when close to the horizon, and twinkle less as they rise above the horizon. I suspect whomever wrote the density comment about the sun's early appearance may be confusing the two effects. Hint: I've discussed these issues/effects with other scientists for over 35 years, and 80% to 90% don't really correctly understand these spectroscopic and geometric effects... do these explanations help??? or are they too technical? I've attempted to reduce the associated math and physics to their bare minima. 201.160.124.221 00:59, 20 March 2007 (UTC)The Good Doctor Fry

Finally, I've removed the reference to Fuller's neologisms, since in they appear on the web almost exclusively in mirrors to Wikipedia content, or are the names of companies producing (e.g.) sunglasses or packaging products. I'll be updating the appropriate redirects.

Cheers, Ben Cairns 03:17, 28 Jan 2005 (UTC).

To answer my first question, yes, it can be true. Since times don't change much around the solstices (daylight savings having started or ended in Spring or Autumn), although the actual time differs between locations in a time zone, the latest sunset at one place will be the latest sunset everywhere (or, more-or-less). I still don't understand how this works, exactly, but I can see that it might be possible... but a reference would be nice! Ben Cairns 00:44, 31 Jan 2005 (UTC).

Reply: the latest sunset at one place is not the latest sunset everywhere, (please see the more detailed explanation above) due to the 1.) curvature of the earth and hence it changes as a function of your latitude; 2.) the 23 degree tilt of the earth's axis; and 3.) the elliptical shape of the earth's orbit around the sun (see above) - reaching it's maxima at the solstices. Relative overall effect: the latest sunset in 2007 will occur on 6/27/2007 in Fargo, ND, USA and 3 days later on 6/30/2007 in Albuquerque, NM, USA. Finally, I suspect that most people don't consider 3 days the same day more or less... (especially at Christmas), but really, the actual time differences between sunsets during these days are quite small: typically less than a minute, so, for normal people, the date of the latest sunset appears about the same (within a minute) from 6/22/2007 - 7/2/2007 in Fargo, ND and from 6/23/2007 to 7/7/2007 in Albuquerque. helpful?The Good Doctor Fry 17:16, 20 March 2007 (UTC)The Good Doctor Fry

The Sunset Picture is False/hoax

http://www.snopes.com/photos/sunset.asp -- —Preceding unsigned comment added by 165.21.154.114 (talk • contribs) 14:04, 26 January 2006

No, not a hoax - just a composite of satellite imagry. Which is what the Snopes article is saying, and what we say here, both on the image caption in this article and on the image description page. (Also the image discussed on Snopes is actually a slightly different one, but that doesn't really matter). -- Solipsist 13:27, 26 January 2006 (UTC)

Is impossible to have night at est and sun at ovest. the image is a non correct composition and don't show the concept of sunset

Actually, it's easily possible, once you think about it. The sun sets in the west, and sunset is followed by night, which would be to the east of the sun.  — AnnaKucsma   (Talk to me!) 15:37, 21 November 2006 (UTC)

3 Sunsets

Gibbs on NCIS just said there are 3 sunsets: Nautical, Civilian, and Astronomical. Can anyone expand on that?

Strictly, there are three forms of twilight, not of sunset. This should explain the difference between nautical, civil and astronomical twilight. Thefamouseccles 22:57, 3 September 2006 (UTC)

Sky-watch defines 4 sunsets: standard, civil, nautical and astronomical. Similarly, it defines 4 sunrises.

From early to late in the day:

• Astronomical sunrise — Time when the sun rises higher than 18 degrees below the horizon and when the sky ceases to be totally dark.
• Nautical sunrise — Time when the sun rises higher than 12 degrees below the horizon.
• Civil sunrise — Time when the sun rises higher than 6 degrees below the horizon.
• Standard sunrise — Time when the sun rises above the horizon. This is the value usually published in local newspapers.
• Standard sunset — Time when the sun sets below the horizon. This is the value usually published in local newspapers.
• Civil sunset — Time when the sun sets lower than 6 degrees below the horizon.
• Nautical sunset — Time when the sun sets lower than 12 degrees below the horizon.
• Astronomical sunset — Time when the sun set lower than 18 degrees below the horizon and when the sky starts to be totally dark.

— Adhemar 14:38, 26 September 2006 (UTC)

Addendum: These correspond with the border times of nautical, civil and astronomical twilight, e.g. civil twilight between civil sunrise and standard sunrise.

Gallery

Wikipedia:What Wikipedia is not explicitly states under Wikipedia is not a mirror or a repository of links, images, or media files Point 4.:

Collections of photographs or media files with no text to go with the articles. If you are interested in presenting a picture, please provide an encyclopedic context, or consider adding it to Wikimedia Commons. If a picture comes from a public domain source on a website, then consider adding it to Wikipedia:Images with missing articles or Wikipedia:Public domain image resources.

Most of the pictures have either no caption, or pathetic ones like Yellow sunset, Purple sunset etc. So I'll remove the gallery section again and ask you not to revert it unless you can present compelling arguments why the official policy should not be applied in this case. --Dschwen 12:37, 3 May 2006 (UTC)

I did some pruning again. Yes, it is tempting to add more and more pics to this article in particular, since taking pics of sunsets is easy and they look always pretty (well, almost). But are they adding fundamentally to the understanding of the concept of a sunset? No! Just axe them vigorously! --Dschwen 17:08, 30 August 2006 (UTC)

Agreed. I asked about this specifically in Village pump so you might want to check out what they said. There needs to be a balance between images and text with the emphasis on the text. That is unless for some reason the article demands otherwise, which this one does not. --Roguegeek 17:33, 30 August 2006 (UTC)

Good, but the replacement you just did was pretty neutral. Before we had two similar looking red sunsets (both featured pics by the way), now we have two similar looking sunsest-over-water pics :-) --Dschwen 18:05, 30 August 2006 (UTC)

Makes sense to me. Feel free to edit. :) --Roguegeek 18:13, 30 August 2006 (UTC)

Yeah I disagree with the image choice, for a subject like this I'd be leaning to use FP's. Particularly since Image:LabradorSunset.jpg is low res and Image:Arizona sunset.jpg is blurry (particularly on the RHS) and to be brutally honest does not show a particularly spectacular sunset. Please comment on the replacements. --Fir0002 06:06, 4 September 2006 (UTC)

Current image choices were no better. Although all images are FPs now (which I think is in no way important and, in a lot of ways, counterproductive and boring... but that's another discussion altogether), two red sunsets are still two red sunsets. I removed one and, instead, replaced it with a sunset over a skyline to break up monotony and repetitiveness of the current selection. --Roguegeek 10:30, 4 September 2006 (UTC)

I really don't see monotony and repeativeness and I would respectfully disagree that the currently selection is "no better" than previous images - I mean they are Featured Pictures ie the community thinks that they are of a high standard. And although I like the replacement (it is afterall an FP), it is one of the few sunset images which can actually be used in other articles, so surely it is better to give other photos placement on this article in preference to this photo illustrating multiple pages. Also, although the scenery is tinged in sunset colors, the actual "sunset" is rather obscure - if it was a shot primarily of the sunset the photographer would have taken more of the RHS of the image IMO. --Fir0002 11:47, 4 September 2006 (UTC)

I was curious as to why my sunset image was removed? It was the one with the real cool cumulous cloud sunset in the skies of Clearwater, Fl. 02:51, 13 December 2007 (UTC) —Preceding unsigned comment added by Bond Extreme (talk • contribs)

Earliest sunset in Northern Hemisphere is December, not January

An edit on 22:33, 18 August 2006 from 81.104.118.2 edited the earliest sunset in the Northern Hemisphere from early December to early January without explanation. This is inaccurate. The original information that the earliest sunrise is in early December is accurate.

The earliest Horthern Hemisphere sunrise in December? I can see that for the earliest sunset — which would be on the Winter Solstice around the 21st. Early sunrises in any winter month — December and January included — seems kinda counterintuitive.  — AnnaKucsma   (Talk to me!) 14:43, 4 December 2006 (UTC)

I think the above author made a typo and meant to say "the original information that the earliest sunSET is in early December is accurate," as that was the content of his or her edit. 68.38.127.175 14:53, 4 December 2006 (UTC)

Link suggestion

As done on the Sunrise page, I would like to suggest the following link to a sunrise / -set calendar with interactive location finder. While I am the site admin, I find it correct, not to set the link by myself. But maybe someone find it worthy: sun.exnatura.org --XN 13:16, 3 December 2006 (UTC)

I think, I will give it a try since it's not commercial and GFDL'ed. --XN 20:20, 8 December 2006 (UTC)

Fuller Family

Who the hell cares what Buckmister Fuller's family calls sunset? 71.102.186.234 00:53, 11 December 2006 (UTC)

Mess

This article is a mess. The "scattering" part of the article especially is full of nonsensical sentences--Energman 12:52, 7 January 2007 (UTC)

I agree. It looks like the article is on scattering. People can read about related parts on other articles. I am also not sure what this page should ideally be telling. Any suggestion? Apoorv Khurasia 09:17, 22 April 2007 (UTC)

In the second paragraph, it seems that the information is a bit jumbled. It's like the article was edited because someone mistook the cause of a sunset's colors to be the result of Rayleigh Scattering when Mei Scattering is actually the cause. It seems that the editor was responding to the mistake rather than fixing the article. Maybe someone who knows more about the subject could rework that paragraph to make it sound less "No, it's not Rayleigh Scattering, it's Mie Scattering." A note could even be included about some often mistaking the cause to be Rayleigh Scattering, but make it less confrontational.

Just a suggestion.

Tbowboy3 02:15, 30 May 2007 (UTC)

I agree with your comments,so, I've edited the section to reflect the scientific view of things, a view that was explained and has been accepted since 1908. See my comments below under "colors" to further explain the science behind the current text.The Good Doctor Fry (talk) 16:55, 11 July 2008 (UTC)

Removed Gallery

Wikipedia strongly discourages galleries especially those that add absolutely nothing extra to the article therefore I've removed the gallery per WP:GALLERY and WP:IG and I strongly urge everyone else to rigorously follow suit in future scenarios. Wikipedia articles are not mere collections of photographs or media files Angel (^T•C) 15:57, 9 October 2007 (UTC)

Yeah, been down that road before (check section above). I will remove any gallery if it gets added again. And history shows it will... :-( --Dschwen 16:34, 9 October 2007 (UTC)

A particular user is persistently re-adding the gallery. As they uploaded one of the images within the gallery, they are clearly biased. Angel ^T 17:54, 10 October 2007 (UTC)

The current gallery features a selection of four images that add significantly to the article - sunset from space, inverted sunset, Martian sunset and sunset with funnel clouds. Do you know any better way to explain an inverted sunset, for example? You talk about policies (mistakenly about NPOV, for instance), but do you also understand the topic at hand?
Also, stop with personal attacks on my talk page. Being so fiery about a sunset is amusing but also unnecessary.--Svetovid 01:06, 11 October 2007 (UTC)

It wasn't a personal attack at all. If you read this talk page (including the section above), you'll discover that the general consensus all agree that the article doesn't need a gallery. If you want your image so desperately shown, add it to the commons which is what you've basically forced everyone else to do in the past whenever they've wanted to add their own personal pieces of media. What's amusing is the tantrum you're throwing over this all. Angel ^T 06:34, 11 October 2007 (UTC)

The picture you are talking about (Iss007e10807.jpg) was taken by NASA and last time I checked I didn't own it; I just uploaded the picture because it's unique.
You still didn't explain how you want to illustrate inverted sunset without a picture. Could you focus on the subject instead of on personal attacks?--Svetovid 10:55, 11 October 2007 (UTC)

You could try writing about it? Something this article lacks is text. And I'm not engaging in personal takes at all. I was merely warning you not to assume ownership of articles which you were doing in reverting perfectly legit edits without joining in the discussion here. Angel ^T 05:55, 12 October 2007 (UTC)

Response to 3O request: I have to support consensus here. With two good pictures of sunsets and a {{commons}} link, you do not need to ignore style guidelines by devoting screen space to a gallery. I would hold back from accusations of bias, though. AGF and all that. The images are interesting, but they easily accessed at commons. If you had more text to support the particular distinctive types of sunset that are shown in the images, then you could add some of the thumbnails to the text in the usual way. Concentrate on improving the article and its text content first. Adrian M. H. 09:39, 11 October 2007 (UTC)

I strongly disagree - there is no harm in a small gallery. Many non-wiki users (ie the general public) will have no idea what the commons link does. As long as the image gallery isn't overwhelming (as admittedly it has been in the past) it can only serve to benefit the article and it's readers --Fir0002 09:50, 11 October 2007 (UTC)

Well, having provided a tie breaker (per the raison d'etre of 3O), I will have to leave you to sort it out among yourselves now. I will point out, though, that the commons link is quite self-explanatory. Adrian M. H. 10:03, 11 October 2007 (UTC)

I see no reason for a gallery when the commons is simply a click away. Galleries, especially on articles as short as this, really make the place look 'overpopulated.' I agree with the rest of the guys opposed to a gallery. There is no need for one.

The commons link is enough. I'm thinking that 3 images might be too many images on the page.jonathon 00:10, 28 October 2007 (UTC)

After more than a month, none of the people who oppose the small gallery with unique images wrote a single word nor suggested how to replace the information it provided. As such, it should be added back as long as editors are unable to replace the provided information. If you oppose the addition, state your solution. Otherwise, your opposition fails on WP:NOT#DEMOCRACY.--Svetovid (talk) 12:33, 22 November 2007 (UTC)

I removed the gallery per what Angel said above. If you're so keen to add your inverted sunset, replace it with one of the existing images in the article all of which display some form of the same kind of sunset as it is. —— Ryan ^(t)•(c) 09:36, 21 January 2008 (UTC)

What do you mean by my inverted sunset?
Anyway, unless you replace the information provided by the gallery, there is no point in removing it..--Svetovid (talk) 10:25, 21 January 2008 (UTC)

Once again, I've removed the gallery per what Angel stated above. The only person who ever disputed this consensus was recently blocked for tendentious editing meaning he refused to contribute to the consensus, instead he saw it upon himself to revert everyone else's contributions without discussing it on the article's talk page. All in all, there is no need for a gallery on this article when there's a commons link clearly visible. For an article as short as this, a gallery just makes it appear cluttered. ——Ryan | t • c 16:11, 26 May 2008 (UTC)

Today's edit by User:Spoon!

While I agree with the removal of the sentences regarding the quadrant that the sunset occurs in because they were false, the last sentence regarding the direction of the sun at sunset on the solstices, seems to be true. I'm not sure about the duration part though, as my planetarium software shows that the duration of day and night change depending on location. - Shiftchange (talk) 10:59, 31 January 2008 (UTC)

Okay, I put that last sentence back. --Spoon! (talk) 20:37, 31 January 2008 (UTC)

Color from Mie Scattering

Both this article and Sunrise include language about Mie Scattering being the cause of the red colors when the sun is low in the sky. However, the Mie theory article contains no mention of wavelength dependence. I've been doing some reading and thinking about the subject, but I haven't been able to verify the statement. Does anyone have a reference to back this up? I'm beginning to suspect the "Mie scattering = red" statements are merely the result of someone's misunderstanding of the phenomenon. This rather cartoonish picture is consistent with my understanding of the phenomena. Spiel496 (talk) 06:21, 9 March 2008 (UTC)

After reading up on the subject, I've removed the language about Mie scattering from the explanation of sunset color, and replaced it with the conventional explanation surrounding Rayleigh scattering. The Mie scattering material here and in sunrise was the sole work of Dr. Steven Fry in October 2006, and it looks like it was just a misunderstanding. Spiel496 (talk) 22:02, 13 April 2008 (UTC)

No misunderstandings nor confusion on my part. The previous statements of this article ascribing the reds and oranges of sunset and sunrise to Rayleigh Scattering are simply not accurate, and not even in accordance with the associated Wiki pages on Rayleigh Scattering, Mie Scattering, and light/electromagnetic energy scattering. I have read the non-Wiki Rayleigh Scattering references used in the previous incorrect edits/text, and it seems to me that the previous editor/author did not understand the physics and mathematics involved, as they mis-applied the information from those sites, by taking diagrams and formulae that are designed for molecular scattering during the daytime (molecules are NOT soot or dust or aerosols). They further compounded their errors by mis-applying said daytime diagrams and formulae and descriptions to the special case of sunrise/sunset conditions with both low-altitude dust & soot particles and solid & liquid aerosols present in the longer light path through the lower earth atmosphere of sunlight grazing the earth at sunrise/sunset. The sunrise/sunset low altitude light path through lots of dusty, sooty air near the earth is the main cause of the reds and oranges.

The Wiki pages on Rayleigh Scattering, Mie Scattering and Mie Theory, and scattering are accurate. Wiki source - Rayleigh Scattering page: "Scattering from larger spherical particles is explained by the Mie theory..." The previous author's supposed Rayleigh sources for this information do not address light scattering from soot and dust and other solid aerosols nor sulfuric acid droplets and other atmospheric liquid aerosols.

Wiki Refs continued: "In contrast to Rayleigh scattering, the Mie solution to the scattering problem is valid for all possible ratios of diameter to wavelength, although the technique results in numerical summation of infinite sums." Another pertinent Wiki Reference: "Rayleigh scattering (named after Lord Rayleigh) is the elastic scattering of light or other electromagnetic radiation by particles much smaller than the wavelength of the light."

For Lord Rayleigh's equation to apply, the scattering particle MUST be roughly 10X smaller than the wavelength of light. This restriction rules out the previous color argument for Rayleigh Scattering. The dust and soot particles that cause the nice red and orange colors at sunrise and sunset are much larger (1 - 100 micrometers) than the short wavelengths of red and orange light (400-500 nanometers) (These particles are 10X - 100X larger, with the 1 um - 10 um particulates preferentially scattering red).

Since a typical dust or soot particle is at least 10 times LARGER than the wavelength of Red or Orange light (violating the 10X smaller relationship required by Rayleighs theory), Mie's equation is the correct application, and I was not previously confused. If you read the current Wiki Rayleigh Scattering, Mie Scattering and Scattering articles, they all correctly concur that light scattering by large particles (like dust and soot) are described by Mie's equation, not Rayleigh's. Yes, tiny air molecules do scatter a little bit of red light, but IF the previous author's statements about the sources of sunrise/sunset colors were correct, AT NOON our sky would vary in colors from reds next to the sun, to oranges, greens, purples moving outward to blue at the horizon.

These facts have been accepted and used by spectroscopists (measurement scientists specializing in measurements involving light) since Mie's original publication on this topic in 1908: “Contributions to the optics of turbid media, particularly of colloidal metal solutions”, Annalen der Physik. This stuff is accepted by and is a part of the training of all well-trained spectroscopists. This stuff is not novel, it is not controversial, and it is not new. The Good Doctor Fry (talk) 17:03, 11 July 2008 (UTC)

Finally, I'm currently living in Mexico and have limited access to library research and publications, so I don't have opportunities to pull up the references from primary sources to further polish this material. I am however interested in Wikipedia being factually correct. Entries should start with accurate content, and then progress to inclusion and references to documented sources. —Preceding unsigned comment added by The Good Doctor Fry (talk • contribs) 16:15, 11 July 2008 (UTC)The Good Doctor Fry (talk) 20:55, 11 July 2008 (UTC)

Good Doctor Fry, you have brought up some interesting points. We should figure out which of these explanations is more generally accepted. In the meantime, I have restored the Rayleigh version, because that explanation seems logically consistent, and there are citations to back it up.

I didn't mean to imply you misunderstood scattering theory, but rather what was being said about this topic. Maybe this will clear up the disconnect: The red I'm talking about is in the unscattered light. If you look directly at the sun at sunset, the disk appears not white, but red. In other words, the blue light is missing. Where did the blue light go? The Rayleigh explanation is that got removed from beam via Rayleigh scattering. Is there an inconsistency with that explanation? (It does NOT predict a red sun at noon, because then the shorter path through the atmosphere makes the effect weaker.) I've understood (perhaps incorrectly) that Mie-scattering was not particularly wavelength dependent. However, once you have a red light source, then clouds or other Mie-regime particles would scatter the red light. Otherwise, I find nothing in the Mie Theory article to imply a color. Spiel496 (talk) 05:10, 12 July 2008 (UTC)

If the previous explanations did not satisfy, please consider this: If Rayleigh Scattering explained the intense reds and oranges of good intensely colored sunsets, then: 1. We would see red in the sky around the sun during the daytime; and 2. There would be really intense sunset/sunrise colors on the horizon each and every morning and evening from the ordinary air molecules that are there every day. Since we only see the intense colors when dust, soot, etc. particles are floating in the sunlight's path, then Mie Scattering best explains the colors, and Rayleigh Scattering provides only a tiny tiny contribution. By using a Rayleigh Scattering explanation, you are ignoring the requirement that the wavelength of the light must be 10X LARGER than the scattering particle, which is just not true, regardless of one's ability to understand or apply the mathematics.

At sunset, the blue light from Rayleigh scattering is still there - (in both the scattered light and in the direct light from the sun) - so, your thinking is not necessarily inconsistent, but you haven't included the eye's inability to distinguish it from the rest of the spectrum. The large amounts of scattered red and yellow light just makes it "disappear" into the overwhelming background of the other more dominant colors (colors that the human eye has a more stronger response). e.g. each of the air molecules in the atmosphere still acts like a little prism, preferentially scattering blue light, but it's overwhelmed by all of the red from larger particulate Mie scattering: where Rayleigh Scattering describes a 1/(wavelength)e4 relationship (the reciprocal of the wavelength raised to the fourth power), the which translates to blue being scattered much more strongly than red for molecules and atoms = a generally blue sky when there is little dust or other large particulates in the sunlight's path. The Good Doctor Fry (talk) 13:19, 12 July 2008 (UTC)

The wording of your point #1, leads me to believe you still misunderstood what I'm saying; you refer to "red in the sky around the sun". I'm talking about red light, unscattered, coming directly from the sun. The effect would be minimal at mid-day.

I can't follow the rest of your post without a picture. Please, for the sake of communication, can you comment on this picture and explain what is inaccurate? Spiel496 (talk) 14:44, 12 July 2008 (UTC)

Hello Spiel496, the website you reference contains the answer you requested, but entered further down in the article: "When the air is clear the sunset will appear yellow, because the light from the sun has passed a long distance through air and some of the blue light has been scattered away. If the air is polluted with small particles, natural or otherwise, the sunset will be more red." This statement is mostly correct, but the authors use of "the sunset will appear yellow" could more accurately say "the sun will appear more yellow and red during sunrise and sunset ...". And then they would have to describe the differences between on-axis light traveling mostly straight from the sun to our retinas vs scattered light in the surrounding sunset.

Re the picture: The picture is only partially complete and hence basically misleading. Why? It is missing the other colors and it's misses particulates and aerosols. By depicting only red and blue, it oversimplifies the spectroscopy, color science, and vision/brain processes. By leaving out particles/aerosols it misses 90%-99% (or more) of the visual effects at sunset/sunrise. (Said another way: yes, the FDA allows peanut butter to contains measurable amounts of rat hair, mouse droppings, etc, but if someone asked you to describe the flavor of peanut butter, would you say "peanuts" or "rodent residues"?)

This diagram supports confusion about the public's perception of colors at sunrise and sunset. As the article partially describes: the appearance of the color of the sun and the sky to our eyes depends on multiple factors: 1.) the spectrum (bands of individual colors) of (sun)light reaching our eyes; and 2.) our eye's and brain's abilities to receive and process those individual colors; but it also leaves out: 3.) the effects of the aperture (iris) and lens of our eyes to control what images are in focus on which receptors in the retina; and leaves out 4. the effects of particulates/aerosols in the atmosphere.

By leaving out the yellow and green wavelengths from the original picture at the top of the article, and by not portraying the relative intensities of each of the different colors, and by leaving out the eye's aperture and lens image processing, and by leaving out the scattering effects of particulates/aerosols, the website presents a partial and hence very skewed image. The last part of the picture could be completed by recognizing the our vision's (retinal receptors & brain processing) effects on net/blended color peak perception, resulting in peak reception the green region.

So, when considering all of this, you have to merge: the raw visible spectrum of the sun, the net enhancement and depletion of colors by atmospheric scattering by air molecules, the angular dependence (or independence) of each type of scattering, the numbers of each type of particle present in the light path between the sun and the viewer, the viewer's ability to focus light, and the viewer's ability to convert that light into electrical signals, which the brain arbitrarily interprets as colors or as just one net color. Overall, we're trying to describe a system that has at least 7 or so variables with just one paragraph or so of explanations = doomed to fail?

These same explanations about Rayleigh scattering and Mie Scattering can be applied to explain why ocean water sometimes appears to be green or blue etc, and why the appearance of the colors of things change as we dive deeper and deeper into water.The Good Doctor Fry (talk) 16:46, 12 July 2008 (UTC)

Good Doctor Fry, you're writing too much. I asked one question, and you're bringing up irrelevant issues like mouse droppings and "the viewer's ability to focus light" -- even the most nearsighted person would see a red sunset. And 1000 words later, I still don't know why the sunlight is red. In the article you say simply "Mie scattering", but that's just a name. Did the other colors get absorbed, or were they scattered away? Spiel496 (talk) 14:42, 13 July 2008 (UTC)

Let me rephrase that last post in a more constructive way. What I preferred about the Rayleigh explanation was that it related the red color to the wavelength-dependence of a fundamental phenomenon -- Rayleigh scattering. Of course, that explanation has little value it is incorrect or if, as I think you're saying, it would get you only to yellow rather than deep red. But the current wording (with Mie scattering) doesn't explain why the sunset is red, as opposed to blue or green. Do the particles preferentially scatter red light? Do they absorb green & blue? Do they scatter green & blue, leaving the red light? We need a sentence or phrase that will bring this together. And, ultimately we need to cite a reference. Spiel496 (talk) 13:43, 14 July 2008 (UTC)

Spiel496, Thanks for your patience with my misdirected or less-than-adequate explanations. First: I have a few very near-sighted friends and some slightly color-blind friends that do not see sunsets or colors like much of the rest of the populace. Since most men have diminished red-green visual sensitivity (slightly red-green colorblindness), I have no idea what you see. Many people see purplish sunsets, due to differing visual ability. And yes, blue is there in the sunset, but just not at levels that most unaided human brains and eyes can see.

Visible light scattering by particles or molecules that are equal to or larger than the light's wavelength primarily scatter light in a forward (low angle) direction (Mie Scattering), with enough wavelength dependence to scatter more red sunlight and some yellow sunlight, and scatter even less green and very little blue. So, the red is scattered better for the size/width of solid aerosol particles (dust and soot) and liquid aerosols present in our atmosphere. [ - Dr Fry]

[I'm going to interleave my responses; sorry to break up Dr Fry's post.] If red were scattered the most, then red would be depleted from the direct sunlight. But that isn't what we see: the direct sunlight is red at sunset. So, your explanation is wrong.

Why wrong? Why would preferential scattering of red in the forward direction be inherently wrong? Scattering does not always absorb light, more often, it enhances some colors over others. Look up references on the iridescence of feathers and look up references on diffraction. Diffraction gratings (like CD technology) preferentially scatter specific colors of light. You seem to have presumed that scattering always removes light, an idea which just isn't supported by scientific findings and practical applications of diffraction and interference phenomena.00:11, 18 July 2008 (UTC)

What seems more plausible is that the particles preferentially scatter shorter wavelengths at large angle (just as with Rayleigh scattering even though they are not strictly in the Rayleigh regime) reddening the unscattered light. Spiel496 (talk) 00:47, 17 July 2008 (UTC)

Again, you have inappropriately attempted to apply Rayleigh Scattering and Newtonian prism based principles to a fundamentally different effect. As I've stated at least 2 times above, the mathematics of Rayleigh Scattering just become inconsequential when the wavelength of light is less than 10X larger than the scattering particle = Rayleigh Scattering and Newtonian prism approaches don't apply to light scattering off of dust and soot and other aerosols.

By repeating your misperception over again, or trying to stretch it to fit your conception, does not make it so. The scientific explanation of scattering of light by large particles did not occur until 1908, solved by Mie, and the reason it was not solved until then was because simple Newtonian treatments would not explain the phenomena. It took 200 more years and Mie's sophisticated manipulations of James Clerk Maxwell's relationships to solve the problem, because neither Lord Rayleigh's nor Isaac Newtons understandings were sufficient.

So, Mie Scattering affects your perceived yellow color of the sun, even at mid-day, since the peak energy of sunlight falls in the blue wavelength range, and falls to a minimum in the red red range. Do you see a blue sun? No, because Mie Scattering of so-called "direct sunlight" shifts your perceived perception to a net yellow. [ - Dr Fry]

Are you claiming that in the absence of atmospheric scattering, the sun would appear blue?

You have parsed my sentences into small pieces that don't stand alone. Clearly the sun wouldn't appear blue to humans - it does appear somewhat blue to less biased observers like instruments & spectrometers. Because of the eye and brain's mixing of all colors, the sun, with peak intensity in the blue, is PERCEIVED by the human eye and brain to be yellow. I have stated several times that the eyes and brain preferentially enhance green-yellow wavelengths and we humans have diminished ability to perceive blue.The Good Doctor Fry (talk) 00:11, 18 July 2008 (UTC)

Funny that astronauts don't mention this. Very cute.00:11, 18 July 2008 (UTC)

Also, according to this plot, except for some loss below 450nm (Rayleigh scattering I assume), the solar radiation spectrum at sea level looks pretty similar to that in space. Besides, who cares where the peak in the solar spectrum is? Whatever spectrum the sun has, we are going to call it "white" by definition. Light looks colored if its spectrum deviates from the 6000K black-body radiation of the sun. Spiel496 (talk) 00:47, 17 July 2008 (UTC)

You've somehow ignored the plot in the Wiki solar article that shows the blue spectral peak. It might be helpful for readers to also see Wiki's plot of vision's absolute response by wavelength with a peak of green wavelength detection of human vision, and I don't believe that the sun looks white to most humans.The Good Doctor Fry (talk)

Your question about absorption doesn't really apply - since there is no absorption like happens between pigments and light. [ - Dr Fry]

On the contrary, my question does apply; the answer just happens to be "no". Spiel496 (talk) 00:47, 17 July 2008 (UTC)

No, absorption is a fundamentally different phenomenon, and the term absorption just doesn't apply here in the preferential forward scattering of red light by Mie Scattering. "Google" diffraction of light to see pictures of how scattering can preferentially scatter/enhance some wavelengths, while not transmitting others. "Not transmitting" by cancelling them out is NOT absorption. See interference by a single slit, double slits, and multiple slits.

Continuing: Clearly, dust and soot play pivotal roles in creating red sunsets, and scientists agree that Mie Scattering or dipole dipole approaches explain the red in sunsets, since Rayleigh Scattering does not apply to particles like dust and soot that are 10X - 100X larger than the wavelengths of sunlight. You proposed that we look for some consensus opinion, and that's the consensus opinion of of spectroscopists and is fully supported by mathematical evaluations and real world measurements. You're creating the appearance of a controversy where there is none.The Good Doctor Fry (talk) 00:11, 18 July 2008 (UTC)

Scattering is a fundamentally different process than absorption = apples and cumquats. (See: http://www.philiplaven.com/p2.html for color plots of wavelength dependence and scattering angles and http://hyperphysics.phy-astr.gsu.edu/Hbase/atmos/blusky.html#c5 for pictures/diagrams of direction of light scattering.) Mie Scattering is mostly forward scattering with red dependence for our Earth's size of air particulates, and can be thought of in terms of light bending around the opposite edges (see Huygens Principle) of a spherical particle, creating interference patterns mostly in the forward direction (with the most constructive inference taking place at low angles < 10º), with the typical width/size of dust & soot giving interference patterns that constructively superimpose in-phase waves for red and destructively superimpose blue waves out-of-phase = like two water waves passing each other to either cancel-out or add together, depending on their wavelength. [ - Dr Fry]

If the wavelength dependence is due to constructive and destructive interference, as you claim, then the spectral features would scale with the only length scale in the system -- the particle size. In other words, if the particles shrink by a fraction of 550/650 (the ratio of green to red in wavelength) then the scattering peak would move to the green, rather than red. However, the particle sizes in natural aerosols tend to have log-normal distributions with geometric standard deviations of about 2, meaning the particle sizes vary by a factor of 2. Any wavelength dependence due to interference would be completely smeared out. So, I don't buy this part of your explanation either. Do you have a source to back it up?

As I clearly stated, "the red dependence ... "can be thought of in terms of light bending". You've taken my attempt at presenting a simplified explanation and inappropriately attempted to meet your semi-mathematical approach. As I previously suggested, this is a complex problem that requires very high level mathematics and physics tools to understand.The Good Doctor Fry (talk) 00:11, 18 July 2008 (UTC)

Furthermore, I doubt that low angle scattering is very wavelength dependent. A red sun on the horizon is surrounded by red glare (low angle scattering) and a white sun at mid-day is surrounded by white glare. A simpler explanation is that the low-angle scattered light is simply the same color as the source. Spiel496 (talk) 00:47, 17 July 2008 (UTC)

Please "Google" Mie Scattering and Mie Theory and read the mathematical and physics treastices for yourself. The physics websites clearly identify the wavelength dependence. Further, you can "Google" diffraction gratings and interference to get pictures of how interference works for scattering light. Only a small part of light scattering is explained by simple prisms and sunlight. I've made my best attempts to explain, many parts of which you have chosen to ignore.The Good Doctor Fry (talk) 00:11, 18 July 2008 (UTC)

Sunlight's peak energy intensity (think watts) occurs in the blue part of the spectrum, but because of the combined influences of the slightly wavelength dependent Mie Scattering of "red-enhancing" sized particles and our wavelength dependent eyesight (peaking in the green - see Wiki's lower plot in "color vision"), we see a primarily red sunset with some yellow components = some peach colors.

I have resorted to simplified descriptions (like the peanut butter analogy), since the beginning mathematics of Mie Scattering are based in Maxwell's equations and become successively more complex as they are developed into Mie's final relationships. It's a complex subject whose understanding is typically only first attempted by 2'nd or 3'rd year graduate students in spectroscopy = 2-3 years of additional study for most chemists and physicists, 3-4 years of study beyond the comprehension of physicians and mathematicians, and 4-6 years of study beyond the comprehension of biologists, especially when you try to include multiple wavelengths of light, multiple particle sizes, and non-spherical particles with varying indices of refraction. Tough stuff... So, maybe you'll never understand why sunsets are red, until you study enough physics, chemistry, and math to be able to understand, manipulate, and apply Maxwell's Relationships. [ - Dr Fry ]

It is not wise to assume that because one asks naive questions and avoids jargon, he doesn't have a strong background in physics and math. Spiel496 (talk) 00:47, 17 July 2008 (UTC)

Wisdom has little to do with this, since earlier you rejected my mathematical explanations and you instead requested "pictures". What else should a rational person presume? Since you imply that you have such expertise, then please read Mie's original paper, and interpret it yourself, and report back the results of your personal evaluation. Better still, use Maxwell's Relationships to prove your arguments. Maybe you can disprove Mie and 90 years of subsequent of spectroscopy.The Good Doctor Fry (talk) 00:11, 18 July 2008 (UTC)

I suspect that a high school Physics level of understanding of constructive and destructive interference by multiple slits, blended with an understanding of Huygen's Principle (light bending around corners), is the simplest approach to a simple understanding of Mie Scattering and red sunsets and sunrises. No se.

That's why I earlier stated that full understanding of this topic requires simultaneously juggling 7 or more non-linear higher order variables, where most humans have difficulty understanding or manipulating just 2 or 3 variable systems. Good Luck! 189.202.16.28 (talk) 16:04, 14 July 2008 (UTC)189.202.16.28 (talk) 16:09, 14 July 2008 (UTC)The Good Doctor Fry (talk) 23:53, 14 July 2008 (UTC)

Yes, a full understanding would require a lot of math. But this phenomenon is pretty coarse; light starts out white and ends up red. I cannot believe that omitting some "non-linear higher order terms" is going to throw off some balance and lead to a prediction of green sunsets.

For the article, all I'm looking for is an explanation that says something like "particles in the atmosphere preferentially scatter shorter wavelength green and blue light, leaving just the red." Is that disputed by a reliable source? Spiel496 (talk) 00:47, 17 July 2008 (UTC)

I currently live in a remote area of Mexico, and have limited access to sources other than the internet, to which you have the same access. Yes, if you do some simple leg-work with "Google", you can find physics literature that use a different explanation: Mie Scattering. I could find no "disputes" of your points, because your points were resolved to the satisfaction of scientists by Mie in 1908. Again, simple prism based models scattering green and blue off into space just don't apply. Apples and cumquats. Physics, Chemistry, and Spectroscopy have moved beyond simple Newtonian physics, and hence, some things cannot be explained in Newtonian terms or by Newtonian mathematics like you have proposed.The Good Doctor Fry (talk) 00:11, 18 July 2008 (UTC)

Did I sneak the words "Rayleigh" or "prism" into that sentence somewhere, because I don't see them. My proposed explanation does not rule out Mie scattering; I'm simply identifying which wavelengths are scattered more strongly and how that relates to the sunset color. I did a search as you suggested. Every published source I found supported my proposed wording from 17 July.

• From The Science of Color, by Steven K. Shevell, Optical Society of America, Elsevier, 2003, ISBN:0444512519:

  ...the orange to red color of the rising and setting sun also results from the removal of the shorter wavelengths by scattering.

• From Field Guide to Atmospheric Optics: V. FG02, by Larry C. Andrews, SPIE Press, 2004, ISBN:0819453188:

  Shorter-wavelength sunlight is therefore scattered more out of the beam by the additional aerosols and particulate matter, leaving only the longer red wavelength to get through to the observer.

• From Atomic and Molecular Spectroscopy: Basic Aspects and Practical Applications, by Sune Svanberg, 2004, Springer, ISBN:3540203826:

  The sun emits essentially "white" light. Blue light is scattered more effectively than red and so red light is transmitted better when the angle at which the sun shines is small.

:And yes, they all point out that much of the scattering is due to aerosols with size comparable to the wavelength and is therefore in the Mie scattering regime. Spiel496 (talk) 05:39, 18 July 2008 (UTC)

Spiel496: Good Stuff! First, I'm glad you've come around to understanding that Mie Scattering and Mie Theory (or better still the discreet dipole approximation) best describe sunsets and sunrises, versus the minor player: Rayleigh Scattering (as you and others previously and repeatedly edited Rayleigh scattering into the Wiki sunrise/sunset entries, and edited out Mie Scattering, creating incorrect Wiki entries over the past 2 years), and this hopefully confirms for you and others the that my repeated edits of the Wiki Sunset and Sunrise articles correctly ascribe the majority of the intense red color effects to Mie Scattering or discreet dipole approximation.

Second: No, you did not specifically sneak "prism" into your queries and proposed explanations, but you did continue to inject Rayleigh ( "just as with Rayleigh scattering" ) into your explanations, and your prior proposed explanations and your attempted refutations of my crude analogies used prism-like Newtonian explanations and understandings.

Third: I think the remaining point hinges on semantics or sloppy use of terminology by the cited authors: where the red is actually scattered to the viewer, and blue and green are simply not scattered as intensely (either sloppy or incomplete English by the authors you cited, or an incomplete understanding by said authors, or that by quoting single sentences extracted from the overall context means that additional important information is missing?). Do these authors give mathematical proofs or explanations to support their claims? The reds and oranges at sunrise and sunset are not due to simple transmission of red by a medium that is transparent to red, but instead it is due to scattering of red by larger aerosols (1 um - 100 um) across the sunset to the viewer's eye. If the blue and green scattering off at other angles were the dominant effect, then the blue and green would be seen by humans from particles far to the left and right of the sun at sunset and sunrise. When there are sufficient aerosols/particles in the air, the colors appear fairly uniformly reddish-orange across the whole span of the western horizon, with no blues and greens as the viewer looks at greater angles away from the sun and approaching the periphery. These peripheral and near peripheral particles still are scattering red, and not scattering blue and green (where the air molecules in the sky preferentially scatter blue). There is not some prism-like effect where the red is beamed into outer space to create a blue daytime sky, the red is just not scattered as efficiently as the blue by air molecules. If the authors of these texts actually promote these views, then they are simply mistaken or poorly wording their views, or they do not seem to understand the fundamental processes of either Rayleigh or Mie Scattering.

If they did understand Rayleigh Scattering and Mie Scattering or the discreet dipole approximation, they would not be giving a Rayleigh-like explanations of aerosols scattering blue, instead they would attribute the red appearance to Mie Scattering or to the discreet dipole approximation of scattering red light to the viewer. - the absence of any mentions of Mie scattering or discreet dipole approximations in your quotes speaks volumes about what they've missed. Lot's of Physics texts, Chemistry texts and Biology texts contain errors that are copied or repeated by subsequent authors, propagating the errors forward, especially in general texts. Do they support their claims with mathematical proofs or physical measurements, or do they just make general statements. This type of error is particularly common when authors try to explain complex subjects to the general public, and especially when the authors have a limited understanding themselves. The mathematics here are extremely sophisticated (I can't reproduce them or explain the derivations), but I trust Mie's final results, and those results predict scattering of red by spherical aerosols of 1 um to 100 um, while blue and green are not scattered - not propagated - and hence are not seen.

We see the scattered light, whether it's the blue that's scattered by air molecules or the red that's scattered by larger aerosols (hence my assertion that the authors you quote have incorrectly described the phenomena). Examine the math for yourself. The [discreet dipole approximation] appears to be an even better tool for mathematically describing preferential scattering of red light by irregularly shaped dust and soot particles, it gives similar practical results to Mie Scattering, but I am not familiar with the discreet dipole approximation. The Good Doctor Fry (talk) 14:41, 18 July 2008 (UTC)

Here's the address of a fairly basic article describing how to use the Mie (Lorenz) theory for real-world applications: http://graphics.ucsd.edu/~henrik/papers/lorenz_mie_theory/computing_scattering_properties_using_lorenz_mie_theory.pdf . The authors spend 4 pages outlining the basic math involved in real-world applications.

I offer this to demonstrate why your previous assertions like: ":Yes, a full understanding would require a lot of math. But this phenomenon is pretty coarse; light starts out white and ends up red. I cannot believe that omitting some "non-linear higher order terms" is going to throw off some balance and lead to a prediction of green sunsets." Every treatment I've read on this hardly characterize these phenomena as "pretty coarse". Your attempts to oversimplify a complex phenomenon have consistently led you to inappropriate presumptions and incorrect conclusions. For the benefit of other readers, review the authors first steps from page 4: "The Lorenz-Mie coefficients an and bn in Equations 2 and 3, are composed of the spherical Bessel functions jn(z) and yn(z) in the following way: ..." followed by 2 fairly "hairy" Bessel functions. [ - Dr Fry ]

Pardon? That's a lot of math, and the authors don't get around to talking about sunsets. Look, I'm not saying the math is simple. I'm saying one is able to observe only coarse structure in the spectrum. When someone's car has been crushed by a falling rock, he might be interested to hear that gravity was involved, but he's not going to think it relevant to hear about general relativity, Intrusions, and the path integral formulation, even though those topics are required for a full understanding of what happened. Spiel496 (talk) 15:27, 20 July 2008 (UTC)

Here's another pertinent web reference: http://web.missouri.edu/~speckan/witch-stuff/Research/chapter4/node10.html . In which the author clearly refutes your earlier assertions that Mie Scattering and its results are (not) wavelength independent: "Mie theory describes the way in which spherical, homogeneous particles interact with electromagnetic radiation. Certain assumptions are made about these particles in order to simplify the situation. ... 2) The optical properties of the particle are completely described by frequency-dependent optical constants (i.e. the complex refractive index or the complex dielectric function)." Note that this author confirms my assertions about the frequency dependent nature of Mie Scattering in sunsets and sunrises.

Here's a web address for a Mie Scattering calculator: http://omlc.ogi.edu/software/mie/ . Applying this calculator for red vs blue wavelength for 1 um particles gives a red scattering efficiency that's 60% larger for red @ 660 nm vs blue @ 475 nm in forward directions. If your listed references were correct, why is the blue scattering efficiency so much smaller than for red (even though each blue photon has roughly 72% higher energy).? This actual calculation shows that red wavelengths are scattered much better by small atmospheric aerosols than blue. If you need to prove this for yourself, Enter: 1 um particle size and 0.660 um for red and hit "Go". Read the answer for scattering efficiency in the resulting box. Try the calculation again with 0.475 um for blue. These real world values show that red is scattered 60% more efficiently than blue by typical atmospheric spherical particles, regardless of what your references hypothesize or postulate.

Finally, if the air near the earth's surface (troposphere) contains no particulate matter, then Rayleigh scattering is the predominant phenomenon, where blue is scattered off in all directions 3.72X more efficiently than red, and the long sunset/sunrise atmospheric light paths deplete blue from the sun's spectrum, but how many times are there no particulates in our air? The red colors of particulate-free atmospheres are pretty wimpy. Also, if aerosol/particulate scattering were not the dominant factor in well-colored sunsets, then why is each sunset some different from the last - where the same number of air molecules (scattering blue) is basically constant from day to day, (ignoring minor thermal lensing effects & density variation effects), versus the widely varying day-to-day particulate/aerosol content. And how often are red sunrises more intense than sunsets? The number of air molecules are the same. But because sunset tropospheres routinely hold more dust and aerosols than sunrise tropospheric paths, sunsets are generally more intense than sunrises. And don't we all prefer the beautiful red-orange-peach hues of a dust-laden Southwestern US Arizona or New Mexico sunset, versus the barely-red sunsets that occur after rain-showers wash out the particles?The Good Doctor Fry (talk) 19:26, 18 July 2008 (UTC)

Cool website (omlc.ogi.edu). I'll play around with it. In the meantime, can I just point out one thing? Earlier, you wrote that I " seem to have presumed that scattering always removes light, an idea which just isn't supported by scientific findings". Look at the results generated by http://omlc.ogi.edu/calc/mie_calc.html . It reports a scattering coefficient and an attenuation coefficient. For non-absorbing particles (real refractive index) the attenuation and scattering coefficients are always equal. In other words, scattering always removes light. That is the point I'm trying to make. I'm not disputing that aerosols are the cause of red sunsets. If you write another 200-word paragraph about particles, I swear I'm going to gouge my eyes out with a fork. All I'm saying is that in order for the sun to be red, the blue and green must have had more attenuation than red and therefore more scattering than red. Spiel496 (talk) 05:27, 19 July 2008 (UTC)

OK, I tried the Mie calculator you pointed to. It's true, for 1.0um, red scatters the most, which was surprising to me. However, I also found that it oscillates with particle size: for example, 1.4um particles and those smaller than 0.6um scatter more blue than red. So, it's difficult to draw conclusions without a lot more analysis, which would constitute original research.

Bottom line, I have presented three references from reputable publishers that say sunsets are red because shorter wavelengths are attenuated by scattering. Your counter-argument appears to be that these sources are wrong. Well, the threshold for inclusion in Wikipedia is verifiability, not truth. I hate to fall back on the verifiability argument, because I think it's sometimes used to justify content from bogus websites. But in this case, I don't know what else to say. Spiel496 (talk) 15:27, 20 July 2008 (UTC)

Oh well. The other related Wiki articles and their references clearly identify that Rayleigh Scattering only applies when the wavelength is 10X or more larger than particle size. Further they point out that Mie Scattering or the discreet dipole approximation applies when the light wavelength is comparable to the particle size. [-Dr Fry]

No one is saying that it's Rayleigh scattering. Stop putting words in my mouth. Spiel496 (talk) 16:45, 21 July 2008 (UTC)

Since sunrises and sunsets do not consistently have the same colors and intensities, due to the main variable: the atmosphere's solid and liquid aerosol content (dust, soot, and volcanic aerosols), rational thought, logic, and expert opinions would seem to dictate the current blended explanation entered last week:

"The intense red and orange hues of the sky at sunset and sunrise are mainly caused by scattering of sunlight off of dust particles, soot particles, other solid aerosols, and liquid aerosols floating in the earth's atmosphere. These enhanced red and orange colors at sunset and sunrise are mathematically explained by Mie theory or the discrete dipole approximation. When there are no particulates in the troposphere, such as after a big rain storm, then the remaining less intense reds are explained by Rayleigh Scattering of sunlight off of air molecules."

Until texts or references with more comprehensive and more accurate descriptions can be found, I propose that the text be left as is: since it both has appropriate references and is factually correct. I don't see any controversy. Does Wiki-land have no room for mathematics and precise results? Must we have a reference that says: 2 + 2 = 4 to qualify for Wiki-land? Mathematical results and 100 years of acceptance and application of a theory (with no substantive intervening challenges) should qualify for something. The current references I listed above support the explanation I entered. If Wiki entries on complex topics must devolve exclusively to (inadequate or incorrect) dumbed-down published references for topics that the 99.99% of the public cannot understand (like the articles on Mie Theroy), then it's a pretty flawed affair for scientific and mathematical topics, particularly ones that require profound and sophisticated knowledge of mathematics and physics. This approach makes Wiki inherently untrustworthy in these areas? I hope there's a better answer out there than these conclusions. Any suggestions? The Good Doctor Fry (talk) 17:16, 20 July 2008 (UTC)

The current wording is still inadequate, because it does not relate the color of the sunset to the wavelength dependence of the scattering. Spiel496 (talk) 16:45, 21 July 2008 (UTC)

The text of the section on sunset colors was again mistakenly changed to attribute the main sunset colors to wavelength dependent Rayliegh Scattering vs. the correct scientific application of Mie Scattering or Dipole interations. As stated repeatedly above, Rayliegh Scattering only applies when the scattering particle is 10X or more smaller than the wavelength of the incoming light. Dust, soot, and other aerosols that cause the intense reds and oranges of sunset and sunrise are much larger than the wavelength of visible light from the sun. Further, light is not "scattered off" particles and molecules, it is "scattered by" them.

If you disagree with these points: then why do we only see these intense reds in the sky during sunrise and sunset or when fires choke the daytime sky with dust & soot. If Rayliegh Scattering were the main explanation for the reds and oranges, then we'd see reds and oranges throughout the day, even on clear days. It takes the long pathlengths of sunlight at sunrise and sunset passing through lots of air containing aerosols to create the appearance of red and orange - or in smokey dust/soot laden air during fires. Please read the paragraphs above that describe these reasons and facts in great detail, before editing the "Colors" section to include incorrect, partial explanations.The Good Doctor Fry (talk) 01:05, 28 March 2009 (UTC)

The Good Doctor Fry, you said your piece several months ago. I was never able to understand your objections, and no one else felt moved to chime in. I don't think other editors want to see us restart that long-winded discussion. I would be glad to discuss it on my talk page or yours. If you insist on using this article's Talk page, please start a new thread at the bottom. Be concise. Don't bring up peripheral topics (like "scattered off" vs "scattered by"). Discuss specific phrases from the article or from posts on the Talk page.

Now, regarding your edit yesterday. I am reverting it for the following reasons:

• Your justification for deleting material was that it attributed the colors to "Rayleigh scattering". Check the original yourself; it makes no mention of Rayleigh scattering. I conclude therefore, that you didn't read the material carefully enough before deleting it.
• You used verbose and redundant wording. For example, "dust particles, soot particles, other solid aerosols, and liquid aerosols" when simply "airborne particles" would suffice.
• My material relates observed colors to the wavelength dependence of the scattering; yours does not.
• My material cites references. Yours does not.

Spiel496 (talk) 00:48, 29 March 2009 (UTC)

Spiel: your recent edit again re-instated a line of thinking that a single mechanism explains both a blue sky and a red sunset. This is just not factually correct, regardless of your citations of references. Blue sky color comes from a somewhat radial preferential scattering of shorter wavelength blue light by air molecules: Rayleigh Scattering. The intense reds of sunsets come primarily from a low angle forward scattering of red light by particulates and aerosols: Mie Scattering. Your explanations ignore this angular dependence and instead mistakenly focus solely on a single misapplied wavelength-dependent model.

Your attempts to force your view of things created a factual misperception that at single process can describe both blue sky and red sunset, which is simply false. The same processes that produce a blue sky simply do not drag and drop in a single fell swoop to properly explain sunset colors. Sure, both phenomenon involve scattering, and both are wavelength dependent, but the two processes do not have anywhere near the same types of wavelength dependence nor do they have similar angular dependence - which your edits continue to incorrectly promote. Please read more sources, study Rayleigh Scattering in depth, and study the Bessel functions of the Mei theory to further understand the flaws in your proposed mechanisms.

If blue were being preferentially scattered out into space at sunrise and sunset by dust particulates, other solid aerosols, and liquid aerosols, then the regions of the atmosphere where there is sunrise and sunset would look more intensely blue when viewed above from space, which they do not. You may cite all the references you like, but either you're improperly paraphrasing them, or the authors you quote just don't know atmospheric spectroscopy, or describe it poorly. The Good Doctor Fry (talk) 22:03, 14 April 2009 (UTC)

I note that Spiel continues to edit the colors section of this article, using scientifically incomplete (hence factually incorrect) explanations of the intense reds and oranges that occur at sunset. He has not yet scientifically or mathematically supported the overly-broad and hence incorrect assumptions - leaving the issues/problems that I identified above, unaddressed. I suspect that he has relied on claims of verifiability, substituting (poorly paraphrased or misunderstood?) sources to support his incomplete understandings of scattering: where the single explanation of wavelength dependent scattering cannot and never has explained both a blue sky and red/orange sunsets. The complex mathematics involved in Mie Scattering elude easy explanations, leading to continued incomplete & incorrect edits this section to fit a limited understanding of a beautiful phenomenon. Nothing personal, but this appears to be a fundamental weakness in Wikipedia, where anyone with access to Wikipedia can edit and remove factually verified and scientifically accepted explanations, replacing them with overly-simplified incorrect but potentially self-satisfying solutions.

A novice reader of the subject of sunset colors would be best served with a Wiki article that includes both molecular (Rayleigh) and particulate/aerosol (Mei) scattering descriptions as the causes, since it takes both scientific models to explain all reds of sunsets and the blue sky. A single 'wavelength dependent' explanation of depleted or enhanced blue light is neither correct nor complete. e.g. there is not a predominance of blue scattered upward into space above sunrises/sunsets (as proposed by particulates scattering blue off at other angles), nor is there a predominance of a red halo around the sun during daytime due to low angle aerosol/particulate-based scattering. The daytime sky colors are a result of sunlight's short atmospheric path lengths and somewhat radial Rayleigh scattering by air molecules, and the intense reds and oranges of sunset/sunrise are mainly due to forward scattering of reds through long atmospheric pathlengths. The Good Doctor Fry (talk) 15:56, 22 April 2009 (UTC)

Intro Too Long

I added the template for the introduction being too long because I don't have time to edit it. Icefall5 (talk) 19:51, 7 May 2008 (UTC)

Invalid photo

If sunset "is the time at which the sun disappears below the horizon in the west" then why does the 1st photo show the sun clearly visible? This is obviously not a photo of a sunset according to the intro paragraph. The sun has not disappeared if you can clearly see it in a photo. Either the definition is incorrect and needs to be changed or the photo is incorrect. It can't be both ways. I'm going to replace that invalid photo with one that coincides with the opening definition. - Marc Averette (talk) 21:46, 7 May 2008 (UTC)

This strikes me as just a tad nit-picky. I would say "sunset" has multiple meanings. It can mean the moment the top edge passes below the horizon, but it also refers to a wider period of time. For the photo, isn't two minutes before sunset close enough? Spiel496 (talk) 03:56, 8 May 2008 (UTC)

If it is, then the definition needs to be changed. That's the whole point of this. - Marc Averette (talk) 02:18, 10 May 2008 (UTC)

I get it. The definition gives the precise moment of sunset, but the photo was two minutes early. So now you've replaced the photo. Can you really guarantee that the new one (Miamisunset2004.jpg) is timed closer to the moment of sunset? If not, then I don't understand how it improves the situation. Spiel496 (talk) 22:18, 10 May 2008 (UTC)

I took it; and remember it was just after the sun disappeared. Even though it can't be proven, it at least has the possibility of being correct, whereas the other shot had no possibility of being correct (according to the definition given). - Marc Averette (talk) 01:32, 11 May 2008 (UTC)

I'm leaning towards Spiel496 here. Not only are you being incredibly nitpicky but you admit to owning that photo? So really this is your attempt at trying to showcase your media —— Ryan ^(t)•(c) 10:00, 11 May 2008 (UTC)

I'm not doing anything but following the definition that's given. Your opinion is irrelevant. - Marc Averette (talk) 17:11, 11 May 2008 (UTC)

The definition mentions the sun and the horizon, so I've replaced the photo with the previous one, which shows the sun and the horizon. I dealt with the timing issue by pointing out the timing in the caption. Hope this works for everyone. Spiel496 (talk) 03:14, 13 May 2008 (UTC)

<completely innocent suggestion>I think that using Image:Gull Lake.JPG would be a reasonable solution. No ulterior motives here...</completely innocent suggestion> --Onorem♠Dil 03:19, 13 May 2008 (UTC)

But the sun hasn't disappeared yet. I can still see it. Therefore, it's not a sunset. - Marc Averette (talk) 03:23, 13 May 2008 (UTC)

Fair enough. I didn't really expect to solve the problem with my "innocent suggestion"...I was more trying to point out that discussing a picture you'd like to see in this article is more productive than joining into a long, stupid, slow edit war over it. Discussion is the way to go. If you're really that upset over the current picture, try a request for comment. --Onorem♠Dil 03:34, 13 May 2008 (UTC)

Are any of these three potential pictures acceptable? All 3 images appear have compatible licensing, they appear to meet the definition, and there wouldn't appear to be any conflict of interest in the choice. --Onorem♠Dil 03:56, 13 May 2008 (UTC)

I had forgotten about the follow-up pic to my previous "innocent suggestion," but I'll throw Image:Gull Lake Again.JPG into the discussion for fun. --Onorem♠Dil 04:02, 13 May 2008 (UTC)

Is there anything particularly wrong with the one that's there? I don't understand what the big complaint is here. Why isn't the current one adequate? - Marc Averette (talk) 04:04, 13 May 2008 (UTC)

Marc Averette, I think the problem is that you're failing to make it clear to other editors what it is you wish to accomplish. In your original comment you indicated your desire to make the definition and the photo consistent with one another. That could mean replacing the photo, or rewording the definition to include the colloquial use of the term, or putting a disclaimer on the photo to indicating the time relative to the actual moment of sunset. But rather than discussing this you're snapping at people with terse entries like "it's not a sunset" and the ever-charming "Your opinion is irrelevant." In the interest of figuring out what everyone wants, here are three verbose points:

First, people didn't understand your point that sunset is defined as the instant when the edge of the sun crosses the horizon. (So, to Onorem, that's why the proposed photos don't solve the issue.) I tried to make that distinction more clear in the article by adding what Averette calls "extremely bad and unnecessary wording". I apologize for being such a screw-up. I took another shot at it, but it would be easier to correct the wording if someone would indicate what I did wrong.

Second, I think there's some concern out there that you're making an excuse to showcase your own photo. If that's not the case, then please reassure everyone.

Third, the only evidence that your photo is really taken at the moment of sunset is from your own observation of the event. If we were to get really nit-picky -- and I think it's fair to say we are -- then even the statement that your photo is a sunset constitutes OR. Spiel496 (talk) 05:40, 13 May 2008 (UTC)

Two good reasons to keep current photo. The 1st two dictionary definitions of sunset are:

1. The time of day when the sun disappears below the western horizon. - This obviously states that the sun must no longer be visible in the photo.

2. The changes in color of the sky at sunset. - This suggests that a more representative photo would have changes in color different from the normal color of the sky. The current photo is the most colorful example I've seen on the page so far; another good reason that it's far more representative of sunset than one that's lacking a lot of bright contrasting colors.

Importance of the definition

Whatever the colloquial use of the word is, there is a reason why the definition splits hairs. Sightings of sunrise and sunset can be timed with a precision of less than one second. They can be used in conjuction with precise time and approximate lattitude to determine one's longitude in celestial navigation. For every one second of error in ascertaining the precise time of sunrise/sunset, the calculated longitude will be in error by a quarter mile.

The operational definition as used by navigators, as well as astronomers and scholars is correct. It would be unwise to change it to an incorrect definition just so it agrees with an incorrect picture.--Bodybagger (talk) 10:10, 29 June 2008 (UTC)

Agreed. The current picture is currently the best candidate, since the definition is accurate. - Marc Averette (talk) 16:02, 29 June 2008 (UTC)

Shadow

A unusual phenomenon has been noted that at sunset, say about 6pm, the shadow of a 6-feet human would be undefined (as tan 180° = 0). But 4 minutes earlier, at 5.56pm, his shadow would have reached distance of 352.941 feet (as tan 179° = -0.017) in the direction of east.

This information is important as the processes involved in sunset is different from the sunlight for the rest of the day and not yet fully understood. There are serious gaps in knowledge of what happens in the last few minutes before sunset. Anwar (talk) 19:45, 30 June 2008 (UTC)

See Talk:Sunrise#Shadow. Spiel496 (talk) 05:34, 1 July 2008 (UTC)

What is "sunset" ?

Removing this picture from the article just because the upper limb of the Sun is not touching the apparent horizon was a snobbish and not very smart attitude (doing it when the picture is being evaluated at FPC is ungraceful, to say the least). Yes, I also have a little knowledge of Astronomy and am aware of the astronomical meaning of the word (as well as of the others). Still if we read the text with same care it soon becomes obvious, at the second paragraph, that the article is not restricted to the astronomical meaning. I really don’t think that this kind of agressive editing contributes positively to the project. -- Alvesgaspar (talk) 22:17, 6 September 2008 (UTC)

Aggressive and snobbish editing? I was being polite and constructive. I for one consider this and this to be far more aggressive. I understand that the image in question is your image but your editing behaviour is on the verge of violating WP:OWN. I've already urged you to contribute to the text of the article rather than cluttering it up with images. There is a commons link clearly visible at the bottom. Why can't you upload your image there? —— RyanLupin • (talk) 22:44, 6 September 2008 (UTC)

• My contribution to the English Wikipedia consists mainly in adding good quality images to the articles, not writing them (everyone has his own talents and limitations). Also, I'm well aware of the existance of Commons, that is where I have my main user page. However, I can't understand (and hardly accept) the limited scope you are apparently trying to impose on the definition of "sunset". When we say that the sunset is beautiful (or yellow, or blue, or "magic") are we really talking about the "moment the sun's upper limb touches the horizon" or about the "period of time during which the sun is setting below the horizon? Certainly the second, and a quick reading of the present article should be enough to arrive to this conclusion. That is why I think that the above image is useful and adds value to the text. I agree that the article (and also the image, for that matter) is not mine. But it is not yours either, despite your authoritative attitude. The fact that you chose not to talk about the substance of the debate, the meaning of "sunset", is somehow revealing. Don't worry, I won't touch your article again. -- Alvesgaspar (talk) 23:28, 6 September 2008 (UTC)

Browse through the articles history, you'll notice that I never changed the written definition of a sunset. I confess to not understanding the scientific nor astronomical characteristics of a sunset hence the reason why I didn't make such a change, nor did I revert any of your contributions to the definition. My only concern here is the image you persistently keep adding. Like I said, I see no reason to add it when there are already 3 existing images. I am fully aware that this isn't my article, I'm not claiming ownership in any way here! I'm being constructive and realistic. Does an article that's only 9KBs in size really benefit from having 4 overly large images? —— RyanLupin • (talk) 23:40, 6 September 2008 (UTC)

• Do I see a double criterium here and here? Or maybe the present leading picture is saved from oblivion by its ambiguity? Either the (limiting) definition of the article should be adjusted (I did it once but the correction was reverted) or the present criterium should be applied consistently. I do not intend to touch the article again, but please, let's get serious! -- Alvesgaspar (talk) 17:32, 15 September 2008 (UTC)
  • PS - No need of any expert help to define sunset. Only common sense and intelectual honesty. As everyone can see, the astronomical definition of sunset is not much relevant in the present scope of the article. One last thing: it is not formally necessary to avoid the terms "sun" and "setting" in the definition of "sunset", because those words are not the object of the definition.-- Alvesgaspar (talk) 18:23, 15 September 2008 (UTC)

I was the one who made that comment. I didn't mean to come off as so blunt, and I apologize. I also am in favor of loosening up the definition so that it fits with common sense. I just felt that your wording was a bit circular and, not seeing a simple fix, I went back to the old wording. Spiel496 (talk) 16:37, 16 September 2008 (UTC)

Because having too many pictures has been identified as part of the problem, I have removed the composite image of the terminator. It is not a real picture; no image from space would ever look like this; it implies that the transition from light to dark is more sudden than it really is at the terminator; it is not a sunset. I could go on. Spiel496 (talk) 16:37, 16 September 2008 (UTC)

Regarding the choice of photo for example sunset, I think the article would benefit from a photo that shows the objects referred to in the definition, namely, the disk of the sun and the horizon. The current photo shows neither. Yes, as Averette has pointed out, if you can see any part of the sun's disk then, technically the photo was taken before sunset. My response to that is:

• The caption could be worded to say "two minutes before sunset"; the photo could then be educational, accurate, and pretty
• No photo can be taken exactly at sunset, because the shutter time is nonzero
• Any photo taken "at" sunset, if the sky is clear enough to see the horizon, is simply a picture of the absence of the sun, which doesn't illustrate anything.

I would support a change in the intro photo. Spiel496 (talk) 16:37, 16 September 2008 (UTC)

• Thanks for your explanation. I think that we'll have to define two different things: the phenomenon of sunset, which is basically the disappearance of the sun's disk beyond the horizon, as a result of the apparent motion of the celestial sphere (the present article is really about this phenomenon); and the time of sunset, which Astronomy defines as the moment the upper limb of the sun touches the horizon. I agree that the leading picture should show the sun's disk. -- Alvesgaspar (talk) 16:57, 16 September 2008 (UTC)

Perhaps there should be two lead photos. The first one could show the sun right before sunset, and the second (current one) right after sunset, since there technically is no during, as it's infinitely small. - Marc Averette (talk) 17:48, 16 September 2008 (UTC)

• Let's be constructive. Here is a proposal for a new leading paragraph, to replace the existing one:

Sunset is the daily disappearance of the sun below the horizon as a result of the apparent diurnal motion of the celestial sphere. The period of sunset is commonly taken to begin when the lower limb of the sun touches the horizon and end when it disappears from view. In Astronomy the time of sunset is defined as the moment the trailing edge of the sun's disk disappears below the horizon in the west. Due to refraction of light in the atmosphere, the ray path of the setting sun is highly distorted near the horizon making the apparent astronomical sunset to occur when the sun’s disk is already about one diameter below the horizon. Sunset should not be confused with dusk, which is the moment at which darkness falls, when the sun is about eighteen degrees below the horizon. The period between the astronomical sunset and dusk is called twilight. -- Alvesgaspar (talk) 08:37, 17 September 2008 (UTC)

• • Done -- Alvesgaspar (talk) 10:29, 14 December 2008 (UTC)
    • I would disagree with this, as there is no citation for the line "The period of sunset is commonly taken to begin when the lower limb of the sun touches the horizon and end when it disappears from view." and third party definitions ([1] [2] define sunset as the time after the sun has disappeared below the horizon, which is in contradiction with the claim in this sentence... I think this edit should be reverted until an appropriate citation can be found to support the claim as otherwise it would violate WP:NOR --Fir0002 22:02, 14 December 2008 (UTC)
    • I can't see any third part definition stating that "sunset is the time after the sun has disappeared" simply because that would be wrong. The period between the moment of the apparent astronomical sunset (the upper limb touching the horizon) and the begining of darkness (dusk) is called twilight, not sunset. In all definitions in the literature (including the ones you mention above), the sunset phenomenon refers to the period during which the sun disappears below the horizon. So, it is just a trivial conclusion that, during that period, the sun is visible! Why is a citation needed? Frankly, I fail to understand the reason of your disagreement. -- Alvesgaspar (talk) 22:59, 14 December 2008 (UTC)
      • That is not entirely correct because twilight occurs when the sun is well below the horizon (12 degrees), and is characterised by soft diffused light from the sky hence it's name of "the blue hour". Sunset occurs before twilight and is when the light scattering turns the sky red/orange/yellow which is typically just after the sun has set (when it is less than 12 degrees below the horizon). If you read the definitions carefully they say that sunset is when the sun sets, in other words when it has descended below the horizon. Therefore sunset has not occurred when the sun is still above the horizon. I personally have never heard sunset be defined as the period between the lower edge touching the horizon and the upper edge descending below it, which is why I would like to see a citation for it being "commonly" regarded as such. --Fir0002 09:08, 15 December 2008 (UTC)
        • Not so. Twilight is a period, not a moment. In general, it is the period between the sunset (or sunrise) and the begining (or end) of darkness. Three different types of twilight are defined: astronomical, nautical and civilian. For example, the nautical twilight is that period when astronomical observation of the stars and planets are made on board ships, because it is possible to see both the stars and the horizon. -- Alvesgaspar (talk) 09:56, 15 December 2008 (UTC)
        • Regardless of this definition, I would say that a different but relevant definition of sunset is the "the atmospheric and scenic phenomena accompanying [a sunset"]. This is what I think most people would associate with the word "sunset", eg "I saw a beautiful sunset last night". I think the correct wording of the article should be along the lines of:

Sunset is the daily disappearance of the sun below the horizon as a result of the apparent diurnal motion of the celestial sphere. The atmospheric conditions created by the setting of the sun are also commonly referred to as "a sunset". In Astronomy the time of sunset is defined as the moment the trailing edge of the sun's disk disappears below the horizon in the west. (etc) --Fir0002 09:25, 15 December 2008 (UTC)

• I agree with the proposed text. Both meanings are commonly used and that is one of the things I've tried to say three months ago. In practical terms, this means there is place for two lead pictures, with adequate captions: one showing the sun during its setting, and the other, the atmospheric conditions created by the setting. Next step is chosing them. I suggest that should be done by consensus involving a much broader participation. My proposal for the fisrt picture is this one, with the following caption: Sunset at sea, when the sun is about two minutes from disappearing below the horizon. -- Alvesgaspar (talk) 09:56, 15 December 2008 (UTC)

• Two images is fine by me, but I don't see the need for an image of the sun during it's setting, as this has no real relevance to the definitions at all. And while the second definition does cover your image, personally I think it would be more effective to kill to birds with one stone and have an image of the sun fully set but also accompanied by pretty atmospheric conditions. But yes I definitely agree we should have a broader participation than the two or three currently editing the page. What I propose is to send a message to a dozen or so people who have been interested in the page (find them off the history) and put a note up on WP:RFC (this should represent the "text people") and in addition put a note on WP:FPC talkpage to ensure we have enough participants familiar with photographic considerations. This should, I feel, ensure that the process comes to the best conclusion. After a quick scan through the commons sunset category, I picked out a couple of others which I think will be possibilities, but feel free to add more (but lets try keep it under say 12). --Fir0002 00:53, 16 December 2008 (UTC)

• OK I'm going to take the silence as agreement and will seek further input from the sources I listed above tomorrow unless someone has a problem with this. --Fir0002 08:14, 17 December 2008 (UTC)
• After we have agreed on what sunset is, I can't believe we are back to the beginning! If a single lead image is to be chosen, that would be one showing the sun's disk during sunset (not necessarily my picture, btw), which is the most relevant for the definition. How can you say that showing the sun during sunset has no real relevance for the definition (and showing the beautiful colours has)? When I suggested the inclusion of two images, that was an attempt to reach a compromise solution. If you are using that to force again your own photo into the article, than I must strongly oppose -- Alvesgaspar (talk) 09:12, 17 December 2008 (UTC)

• You've clearly misunderstood then. There a two distinct definitions of "sunset". 1. The time when the sun sets [3] or goes below the horizon [4] (pretty much the Astronomical definition [5]). 2. The atmospheric or scenic phenomena accompanying the sun setting (descending below the horizon) [6]; alternatively the colours in the sky accompanying the sun setting [7]. As far as I can tell, and I'm no expert, the only way you can define a period of sunset, rather than a point in time, is to define it as the period in which def #2 applies. Otherwise the astronomical definition is a single point in time. Therefore the sun being visible has absolutely no relevance - the only thing going for your image is the atmospheric conditions. Personally the only reason I can see for you defining sunset as the period between upper and lower limbs of the sun setting is to force your image onto the page. Note that while your input in these discussions seems to be squarely oriented around getting your image back onto the page, I'm perfectly happy to see any of the images in the gallery below to appear. I just feel the current image is entirely inadequate. --Fir0002 09:56, 17 December 2008 (UTC)

• Apparently you use only the definitions which suit your purpose, ignoring the first and most relevant one:sunset is the setting or descent of the sun below the horizon. So, the most rational way to define a period of sunset is considering the time during which the sun's disk is being cut by the horizon, until its dissappearance (about 4 minutes, but strongly depending on latitude and time of the year). No need of any special knowledge of astronomy or celestial geodesy and navigation (the disciplines where these concepts are really relevant) to arrive to this conclusion, just common sense. Different things are the time of astronomical sunset, the moment when the upper limb apparently touches the horizon, and the twilight, which begins at that moment. Your convenient interpretation applies much more to twilight than to sunset. It should be obvious by now that my main main purpose is not to put my own picture back on the page (probably there are better pictures available, depicting the sun), but to force intelectual honesty into this discussion. Your attempt to reduce the decision to a choice of the most beatiful picture in the gallery is not serious, in my opinion. -- Alvesgaspar (talk) 10:57, 17 December 2008 (UTC)

• (reset indent). We're obviously interpreting that in two different ways because that definition to me means "sunset is when the sun descends (or sets) below the horizion" (ie when it is no longer visible). This definition does not provide a "period of sunset" and even if it did it seems like you've arbitrarily determined this period as the time it takes the diameter of the sun to fall below the horizon. Have you a citation to support this? As otherwise you could argue that the sun begins to set as soon as it makes an angle greater than 90 degrees with the eastern horizon. Again I'm not sure where you've grab the term "time of astronomical sunset" as something distinct from sunset - please provide a reference for further explanation. But most certainly you've got the definition of twilight wrong. Twilight can be defined precisely, but more commonly refers to the time when there is a particular atmospheric light: Twilight: the soft, diffused light from the sky when the sun is below the horizon, either from daybreak to sunrise or, more commonly, from sunset to nightfall. This does not occur immediately after sunset as the pictures in the below gallery prove - you're not going to suggest they depict twilight are you? Anyway clearly we need further input on this because you and I don't seem to be getting anywhere. I think it's time to place a note on WP:RFC... --Fir0002 22:43, 17 December 2008 (UTC)
• An excellent source for the scientific meanings of sunset and twilight is in Bowditch ], an old and authoritative American manual of navigation (fortunately online). There we can confirm that all different twilights begin at (astronomical) sunset or end at (astronomical) sunrise. So, they are periods, not moments. I insist on the "astronomical" just to emphasize the difference between the scientific meaning of sunset (a moment) and the common one (a period, or time of the day). Of course I agree with you that when we say "let's go and see the sunset" we are referring to the whole phenomenon, which includes the progressive setting of the sun below the horizon and the gorgeous atmospheric show that take place before, during and after. In a strict scientific sense, all the picures in the gallery were taken during twilight, except the first, which was taken a couple of minutes before sunset. Then, if we are to respect the strict scientific meaning, then none of the pictures would apply, and the article would be pictureless... That is why I think the best solution is to put two lead pictures: one with the sun descending to the horizon and the other shortly after sunset, at the begining of twilight. Agree, Fir and Averette? -- Alvesgaspar (talk) 20:22, 18 December 2008 (UTC)

• Actually the definition in Bodwitch (for twilight and indeed astronomical sunset) agrees exactly with the definition in the Twilight article and this article... and so your conclusion is quite wrong. There are various scientifically defined sunsets, but none of these are defined as exactly after the upper limb crosses the horizon. Furthermore the common definition (as described in the dictionary source I listed above) refers to twilight being the period when the atmosphere is lit by a particular type/amount of light. The pictures in the gallery below are obviously of a sunset (would you think they have a place in the twilight article?!). Also any of the images in the gallery could illustrate the scientific sense because the sun is below the horizon. Sure the sun could already be 10 mins under the horizon but there's no way of telling that - for all we know (and for all the average reader will know) these were taken at exactly scientific sunset. But they have further value in illustrating the more common definition of sunset - the atmospheric elements accompanying the sun setting. So in short I think we've simply gone another full circle in this discussion and it's time to place a comment on WP:RFC --Fir0002 05:37, 19 December 2008 (UTC)

The text looks good to me except for the lead-sentence phrase "as a result of the apparent diurnal motion of the celestial sphere". To paraphrase, "The sun moves below the horizon because it appears to move." Meaningless, in my opinion. Is there anything lost if we simplify it to "Sunset is the daily disappearance of the sun below the horizon."? Or, possibly, "Sunset is the daily disappearance of the sun below the horizon as a result of the rotation of the Earth."? Spiel496 (talk) 22:32, 15 December 2008 (UTC)

• Yup that sounds like a much better phrasing of it. --Fir0002 00:53, 16 December 2008 (UTC)

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